We will test the hypothesis that the therapies currently employed to treat childhood leukemias and lymphomas (systemic/intrathecal chemotherapy and lwo-dose, 1800cGy, cranial radiation) cause damage to the neuroregulatory centers int he brain responsible for the sex steroid mediated increase in growth hormone production. As a consequence, these individuals produce normal amounts of GH in the prepubertal years but fail to demonstrate the expected increase in GH concentration in response to sex steroids (both endogenous and exogenous).